A system for laser photocoagulation is known from DE 3936716 A1 and DE 10135944.
A disadvantage of the laser photocoagulators described in the state of the art is that spatial laser-beam profiles with heavy “speckle” occur at the point of impact with the fundus of the eye, which is caused in particular by the inhomogeneous intensity distribution of the transverse mode structure. Inside the laser-beam profile, these inhomogeneities result in significant local thermal elevations (hotspots) during the treatment which far exceed the actual coagulation temperature of approx. 50° C. In standard laser photocoagulation, as a result of the heat conduction into the nerve fibre layer, this leads to a significant increase in pain for the patient and in addition to damage of tissue that is worth preserving.
In addition, because of the spatially inhomogeneous short measurement pulses of a few nanoseconds up to a few microseconds, as a result of the thermal confinement (50 μs), considerable hotspots (>100° C. to 140° C.) occur and thus also cavitation bubbles form inside a light-absorbing tissue layer of the retinal pigment epithelium (RPE).
When these cavitation bubbles collapse, pressure transients form which far exceed the pressure transients, produced by optoacoustics, of the temperature-controlled laser photocoagulation and thus render the actual temperature measurement signal unusable.
An object of the present invention is to overcome the disadvantages known from the state of the art.